Batteries are used in numerous types of portable electronic devices including, without limitation, electronic book (“eBook”) readers, mobile phones, laptop computers, and augmented reality devices. The battery capacity of a device determines the effective run-time for that device from the time the battery is fully charged to the time the battery's charge is depleted. This run-time may diminish over time as the battery is repeatedly charged and discharged, due to degradation of the battery that occurs with use. Thus, a battery's capacity may be an indicator of the battery's state of health.
Another potential indicator of a battery's state of health involves battery resistance. Over time, as a battery is repeatedly charged and discharged, the resistance of the battery may increase gradually. This gradual resistance increase may escalate in magnitude as the battery draws closer to the end of its usable life. Additionally, it is possible for a battery to become internally short circuited, which could cause a failure event to occur. An internal short circuit in a battery may be characterized by a decrease in battery resistance. Thus, a battery's resistance may be an indicator of the battery's state of health.